In the following background information is presented relating to methods for screening for the risk of gastric cancer, primarily using pepsinogen I and gastrin-17 determination from a blood sample.
Although the occurrence of new cases of gastric cancer has diminished in the recent years, gastric cancer is still one of the most common malignancies. In Finland, approximately 250 to 300 new cases of cancer/one million people/year are registered. In the age group of people above 50, there are an estimated 2350 cases of stomach cancer, which is about 3 per mille of the age group population (Finnish Cancer Registryxe2x80x94The Institute for Statistical and Epidemiological Cancer Research 1993). In addition to Finland, there is a high gastric cancer incidence in Iceland, South America and especially in Japan.
The prognosis of gastric cancer is usually poor, as there is no specific treatment. Presently the only possibility of successfully treating gastric cancer is its early detection and total removal surgically.
Gastric cancer does not necessarily give any symptoms in its early stages. The late appearance of symptoms naturally delays the patient from seeking treatment. On the other hand, the clinical findings in the early stage of gastric cancer are often non-specific. The primary diagnostic method for gastric cancer is presently gastroscopy and biopsies, cell and aspiration cytology associated therewith. As routine gastroscopies are carried out in order to examine symptoms, such as pain in the upper abdomen or bleeding of the gastrointestinal tract, a symptomatic gastric cancer discovered in this manner is often already far advanced and thus inoperable. Attempts have also been made at improving primary diagnostics with various immunological methods, but no sufficiently specific immunological method has been successfully developed.
It is a primary object to find the means by which it would be possible to identify within the general population easily and with moderate costs those symptomless persons which might be suffering from gastric cancer in its initial stages. After identification these persons should immediately be examined by gastroscopy. At the same time those persons could be identified which exhibit premalignant gastric changes which need to be followed up.
Gastric cancer can be preceded by a number of different gastric diseases or conditions (so called precancerous conditions), which are chronic atrophic gastritis, pernicious anaemia, ventricular ulcer, gastric polyposis and the Mxc3xa9nxc3xa9trier disease (giant hypertrophic gastritis). Clearly identifiable changes of the mucosa are dysplasia and adenoma. The said conditions are associated with an approximate 4 to 5 fold relative cancer risk, as compared to the general population. It has been established that in almost all diseases the risk is mediated over chronic atrophic gastritis.
Chronic gastritis means a prolonged inflammatory condition of the gastric mucosa. The disease can coarsely be divided into the so-called superficial and the atrophic form. In superficial gastritis, the inflammatory cell infiltration is concentrated below the surface epithelium. In case the inflammation progresses and diffuses between the specific gastric secretory glands, one refers to chronic atrophic gastritis. In such a case, the normal glandular structures of the gastric mucosa are at least partly substituted by metaplastic changes.
The relative risk of gastric cancer in patients suffering from atrophic gastritis in the corpus area of the stomach, has been estimated, as calculated from the Finnish cancer statistics, to be about 4- to 5-fold as compared to persons having a healthy mucosa. In addition, there is a risk for falling ill with pernicious anaemia due to intrinsic factor deficiency and B12 vitamin absorption disturbance. In severe atrophy of the antrum area, the risk is even 18-fold. If atrophic changes appear both in the antrum and the corpus area (pangastritis), the risk can increase to even 90-fold (Sipponen, Kekki, Haapakoski, Ihamxc3xa4ki and Siurala 1985).